ACL Race Series main bearings for Nissan Sunny GTI-R (SR20DET)
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Nissan
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ACL Race Series main bearings for Nissan Sunny GTI-R (SR20DET), part number 5M2975H. These support the crankshaft in the engine block, and in a tuned engine, they are responsible for ensuring oil effectively reaches the entire crankshaft.
They feature three layers over a high-strength steel backing: a copper-lead-tin lining, a thin nickel barrier, and a lead-tin-copper overlay, which is the surface that works against the crankshaft.
The upper shells have a full 180° oil groove, while the lower shells feature a partial groove to avoid interrupting oil flow to the connecting rods; the end of the groove is tapered to prevent pressure spikes. Race Series bearings have higher crush and a slightly more eccentric shape than standard bearings, both designed to keep the bearing securely in place and properly lubricated even when the block and rods deform under load.
In standard size, ACL specifies them for a crankshaft journal diameter of 54.956 to 54.980 mm, and recommends an oil clearance of approximately 0.057 to 0.068 mm for this diameter. If the crankshaft has been reground, these dimensions will change.
They do not have the silver-tin finish found on standard bearings, so their dark color—ranging from brown and black to bluish—is the factory finish and does not indicate any defect. ACL advises against polishing the bearing surface to adjust clearance; if more clearance is needed, combine them with the HX version, which provides an additional 0.025 mm of clearance.
Not sure if your crankshaft is standard size? Message us with your engine code and we will help you choose.